1.3.2. Bowel rest

Although the fecal stream is likely to play a role in the pathogenesis of CD, there is no evidence that bowel rest combined with parenteral nutrition may be beneficial in refractory CD [B].

Current theories on the immunopathogenesis of CD emphasize a T helper cell type 1 response probably directed against antigens of the commensal flora. The susceptibility genes so far identified39 are associated with innate recognition of microbial products or epithelial barrier function.40 The over expression of proinflammatory cytokines and increased production of matrix degrading enzymes by fibroblasts and macrophages are probably responsible for ulceration and fistula formation. Bowel rest might influence this process, beneficially41 or otherwise42 by altering intestinal flora43 or changing the immunological responses to it. Lack of intestinal stimulus by food will affect intestinal motility and could predispose to bacterial overgrowth,42 or could result in reduction of intestinal flora.41

A retrospective Canadian study44 suggested that ‘‘bowel rest’’ and parenteral nutrition could be beneficial in refractory CD. The concept seemed attractive because it had long been known that surgical diversion of the fecal stream away from inflamed parts of the intestine could result in reduction in the inflammation, though it ignored the potential importance of food’s trophic effect on the intestinal mucosa. Early clinical trials45,46 of treating severe colitis, both UC and CD, with parenteral nutrition with no nutrients by mouth or via the intestine proved unpromising; while improvement of nutrition was beneficial, no benefit arose from reducing oral or enteral intake [IIA]. The Canadian group’s prospective controlled trial, in which TPN with bowel rest was compared with nasogastrically administered enteral formula or partial parenteral nutrition with food,47 showed no statistically significant difference between the three small groups and suggested that it was the improvement of nutrition that was most important [IB]. Further uncontrolled studies continued to be published suggesting that parenteral feeding as part of a therapeutic package could play a role in Crohn’s colitis.48 Since the early nineties all the emphasis has been on enteral nutrition and its role in primary therapy in CD,49 which has been accepted, particularly in pediatric practice. Though Greenberg et al’s study if anything suggested a slight, non significant advantage for parenteral feeding with nothing by mouth, there has been little work to examine potential clinical benefit from total parenteral nutrition with nil by mouth since. The argument that enteral feeding is as good and carries fewer side effects and lower expense has prevailed. On present evidence this argument holds good. It is unlikely that there will be a controlled trial done with a sample size big enough to demonstrate whether TPN with nil by mouth is (a) marginally more effective or (b) as effective as enteral feeding.

1.3.3. Improvement of growth

Growth is impaired in most children with CD at some stage. Adequate nutrition should be given, but primarily by the oral and/ or enteral route. PN should be used if enteral feeding cannot be tolerated (in addition to the indications given at the start of this manuscript) (B).

Growth failure in CD is the result of the inflammatory response and malnutrition.50 Any treatment which affects either can be expected to have a beneficial effect on growth. Parenteral nutrition has no known advantage in this respect over enteral nutrition – reviewed elsewhere.49 Specific nutrient deficiencies such as zinc, vitamin D for example should be addressed and then appropriate

energy and nitrogen supplied by the simplest, safest route acceptable to the patient.

1.3.4. Improvement of quality of life

Improvement of chronic malnutrition improves quality of life but this is not specific to parenteral nutrition.

Comments: Malnutrition affects quality of life in gastroenterology patients including those with CD.51 Impaired functional status has been observed despite apparently normal nutritional status in patient with quiescent CD.22 Obviously, quality of life may be altered in CD patients who required long-term parenteral nutrition.52 However, long-term home parenteral nutrition may improve rehabilitation and its social components53 [III].

1.3.5. Primary therapy for active CD

Parenteral nutrition should be not used as a primary treatment in patients with inflammatory luminal CD [A].

Comments: Although a few uncontrolled trials showed some benefit of parenteral nutrition in CD colitis, the only prospective trial comparing parenteral, enteral or oral food failed to slow any advantage of parenteral nutrition and bowel rest47 [IB].

1.3.6. Perioperative nutrition

As for other underlying diseases, parenteral nutrition in the perioperative period should be given to prevent or treat malnutrition in patients who are not likely to be fed orally and/or enterally.

1.3.7. Maintenance of remission

Parenteral nutrition is not recommended for maintenance of remission [B].

Patients in whom remission is induced by parenteral nutrition may have a lower recurrence rate if maintained on subsequent artificial liquid diet.54 Continued parenteral nutrition is clearly not a practical approach to maintenance of remission.

1.4. Practical implementation of PN

1.4.1. Which patients should receive PN? When is PN indicated?

Parenteral nutrition is indicated when nutrition cannot be maintained via the intestine in the following situations:

1.Obstructed bowel not amenable to feeding tube placement beyond the obstruction.

2.Short bowel resulting in severe malabsorption or fluid and electrolyte loss which cannot be managed enterally.

3.Severe dysmotility making enteral feeding impossible.

4.A leaking intestine from high output intestinal fistula, or surgical anastomotic breakdown.

5.Patient intolerant of enteral nutrition whose nutrition cannot be maintained orally

6.Unable to access the gut for enteral feeding [B].

Comments: Malnutrition is a common comorbidity that places patients at risk of complications, infections, long length of stay, higher costs, and increased mortality. Malnutrition is frequent in CD patients, thus nutrition support has become an important